The present invention pertains to the palletizing of articles or the formation of stacks comprising ordered layers of such articles, which articles may themselves comprise layered stacks.
Palletizing systems are well known in the prior art and are utilized to build large, generally prismatic stacks of articles into a compact arrangement for shipping. The articles which are palletized also typically have a rectangular prismatic shape and may themselves comprise either unitary packages or stacks of identical layered items. Each palletized stack typically comprises multiple layers or tiers, stacked one atop another, each of which tiers comprises a plurality of rows of articles. The stacks may be formed on and supported by a shipping pallet or may be formed directly on a conveyor bed or other transfer mechanism.
For palletizing systems which are designed to handle articles of different sizes and shapes, it is generally desirable to form stacks having the same outside dimensions, particularly around the perimeter, so that the stacks substantially conform to the area of the pallets on which they are formed, provide uniformity in size and shape for shipping and storage, and can be wrapped or banded with equipment and materials operated in a uniform manner. Thus, it is often desirable or necessary to form tiers of articles in which there are gaps or spaces between adjacent articles or adjacent rows of articles in order that the tier assumes the shape of the outer perimeter of the stack being formed. For space and shape optimization, it is also often necessary to rotate articles 90.degree. about a vertical axis with respect to other articles forming a tier or one of the tier-forming rows.
U.S. Pat. Nos. 2,699,264; 2,997,187; 4,255,074; 4,352,616 and 5,139,388 all disclose systems for forming stacks of articles from multi-article tiers placed one atop another. In each of the foregoing patents, the individual articles are first formed in rows and a plurality of rows are assembled to form a tier. The tiers are sequentially placed atop a pallet or previously deposited tier, or in the case of the system disclosed in U.S. Pat. No. 2,997,187, each tier is inserted beneath a previously positioned tier or stack of tiers. Each of the foregoing patents discloses some means for reorienting or spacing articles with respect to adjacent articles in a row or in a tier.
However, in all of the above identified prior art systems, a single tier is formed at a time and transferred onto the stack with some sort of transfer or shuttle mechanism on which the tier is formed. Thus, during tier transfer, there is an inevitable delay while the transfer mechanism is moving to and returning from depositing the tier on the stack.